Formation of hollow bodies from powdered materials



Nov. 26, 1963 w. 1-. MONTGOMERY ETAL 3,112,166

FORMATION OF HOLLOW BODIES FROM POWDERED MATERIAIIS 3 Sheets-Sheet 1Filed March 8, 1961 FIG. I.

41 W By W array/Mrs Nov. 26, 1963 FORMATION OF HOLLOW BODIES FROMPOWDERED MATERIALS Filed March a, 1961' W. T. MONTGOMERY ETAL \az puic.

5 Sheets-Sheet 2 Au uni/0am SOD/UM 0194 017/05 f Fayre-i I N VEN TORSIll/11.1.09! Fiona/la; fia/vrao/vzfi r TTJH/VEYS 1963 w. T. MONTGOMERYETAL 3,112,166

FORMATION OF HOLLOW BODIES FROM POWDERED MATERIALS Filed March 8, 1961 5Sheets-Sheet 3 FIG.2

IN VEN TOR Wu 1 09M Doe/mm Mam-amen Y Johw l/szvnr Coax United StatesPatent "cc 3,112,166 FOTIQN 0F HULLQW EDDES FRGM POWDERED MATEREALSWilliam Thornhili Montgomery, Ardrossan, and John Henry Cook,Stevenston, Scotland, assignors to imperial Chemical industries Limited,London, England, a corporation of Great Britain Filed Mar. 8, W61, Ser.No. 94,329 Clairns priority, application Great Britain Mar. 10, 1960 6Claims. (Cl. 1859.3)

This invention relates to the moulding of hollow bodies from powderedmaterials by subjecting the powder to the pressure pulse produced by thedetonation of a high explosive.

In our UK. Patent No. 833,673, a method has been proposed for convertingmetal powder into a coherent mass wherein the bounding surfaces of theparticles of the metal have been sufiiciently destroyed to confer uponthe body a substantial degree of continuity of texture, which comprisespositioning a detonatable high explosive of at least sufiicient powerexplosively to transmit pressure to the contents of a watertightcontainer containing the said metal powder, surrounding the saidcontainer and the detonatable high explosive around it by a stemmingbath of liquid, and detonating the said high explosive. This method isapplicable to the formation of ingots of certain metals and alloys whichcannot be conveniently made by the normal fusion method. The method isparticularly advantageous for compacting fine titanium powder to give asolid ingot which can be subjected to further metal working operations.

An object of the present invention is the provision of a convenientmethod for producing hollow shaped bodies from finely divided powders.

According to the invention a process for the formation of a hollowshaped body from finely divided powder capable of being compacted whensubjected to the pressures generated by detonating explosives ormixtures of such powders comprises embracing one or more cores ofnonexplosive yieldable material capable ultimately of being removed fromthe formed body with a layer of the powder contained in a thin-walledcontainer, positioning a layer of high explosive in proximity around apredetermined portion of the outer surface of the powder container, anddetonating the said high explosive. Each core advantageously consists ofa thin-walled container and a filling material therein. The result isthat on detonation of the explosive all the powder adjacent to thepredetermined portion of the powder container surface is compacted toform a hollow body.

The invention also includes hollow bodies so formed from powderedmaterials.

To further illustrate the invention, examples of the application of theprocess to the formation of tubular elements using various combinationsof core and powdered materials will be described with reference to theaccompanying drawings in which:

FIGURE 1 shows mainly in axial sectional elevation the operativedisposition of core, powdered material to be compacted, explosive layerand surrounding water as assembled in Examples 113;

FIGURE 1a is a fragmentary View illustrating the use of a core composedof a liquid as in Example 6;

FIGURE lb is a fragmentary view illustrating the use of a core composedof a gas as in Example 7;

FIGURE 10 is a fragmentary view illustrating the compaction of differentpowdered materials into a single article as in Example 13; and

FIGURE 2 shows in axial sectional elevation the operative disposition ofcore, powdered graphite to be compacted and explosive layer as assembledin Example 20.

The invention is particularly useful in forming hollow 3,1 12,156 lmented Nov. 26, 1963 bodies, for example tubular bodies from finelydivided metal or non-metallic powders. It provides a convenient methodfor the formation of hollow bodies from mixtures of metal powders whichcannot be alloyed by fusion. It is also useful for forming hollowbodies, for example tubular bodies, having a varying compositionthroughout the mass.

In one convenient form of the invention the explosive layer issurrounded by a liquid medium and water has been found to beparticularly suitable.

Metal powders, for example powdered aluminium, titanium, nickel, etc.,and many non-metallic powders, for example graphite, inorganic salts andpowdered ceramic materials which are stable at elevated temperatures,may be formed into hollow bodies by the invention.

The explosive layer may contain any detonating explosive, but explosivescontaining PETN, pentaerythritol tetranitrate, TNT, trinitrotoluene, ornitroglycerine are convenient. A particularly convenient form ofexplosive for this purpose is commercial detonating fuse cord,containing a core of PETN, enclosed in a waterproof plastic envelope.This can be Wrapped helically or otherwise disposed around the metalpowder container to form the required layer of explosive. When this formof explosive layer is used a more even compacting force is obtained fromthe detonation if the explosive is surrounded by a substantial volume ofliquid, preferably water.

Although the explosive layer may be at some distance from the containerof the powder, it is generally preferred to have it in contact with thiscontainer. However, in compacting powder to form relatively thin-walledhollow bodies it is often advantageous to interpose a buifering layer ofsome powdered material which is not intended to form permanently anypart of the final hollow body between the layer of the explosive and thepowder which is to be compacted into the form of the desiredhollow body.This buffering layer may be contained in any suitable thinwalled outercontainer so that the material is in contact with the thin-walledcontainer of the powder to be compacted to form the desired hollow body.This container separating the bufiering layer from the powder to becompacted into the desired body may be for instance of aluminium, paper,cardboard or the like. The use of such a buifering layer avoids thetendency for the formation of cracks in the wall of the desired hollowbody. The compacted material of the buffering layer may be removed byany convenient method, e.g. by cutting, chip ping, grinding, dissolving,burning or otherwise according to its nature.

The core as a whole must be non-explosive and should be of such a naturethat it does not combine to any undesirable extent during the process,with the powder being formed into the hollow body. It should also be ofsuch a nature that the volume actually embraced by the powder requiredto form the hollow body is capable of sudden substantial reductionwhenever the explosion takes place. It will be understood that the coreas a whole must not act as a rigid body during the explosion since thiscould cause the compacted body to crack. The thin-walled container mustitself be readily deformable, and, if its length does not exceed that ofthe body of the powder to be embraced by explosive, its closure mustnormally be easily rupturable or deformable so as to provide an escapefor the [filling by flow from the embraced space when-the explosion isbrought about unless the material of the filling is itself highlycompressible such as, for example in the case of a gaseous filling. Thecore container should not be permeable to the core filling material butit may be of soft material and may be destructible in the process. Whena liquid is used as the core filling material the sudden substantialreduction in its embraced volume is achieved by displacement of aportion of the liquid in a direction trans verse to that of the actionof the explosive following rupture of the core container. With corefillings of powdered solids of easily compressible or fusible characterthe reduction in volume may often be possible without subs-tantialdisplacement of material outside the confines of the original embracedspace occupied by the core. Although gases may be used as core filling,solids which generate gases in large volume or very rapidly under theaction of the explosive, for instance ammonium nitrate, are lesssuitable since the pressure developed by the gases actually within theembraced hollow body form-ed at the instant of the explosion may besufiicient to crack the formed body before the gas can escape from theend of the container. Salts of alkaline and alkaline earth metals ingranular form are usually good core materials, and sodium chloride andmineral barytes give particularly good results' Cores of the latter twomaterials are, however, compacted in the process, and require to beremoved afterwards, e.g. by leaching with water. When a material likehydrated sodium sulphate is used, it dissolves in its water ofcrystallisation during the process and usually flows out of the formedhollow body. This type of core material is therefore often advantageous.

The invention is especially suitable for the formation of tubes havingsubstantially circular cross-section and substantially uniform wallthickness. Such tubes are formed according to the invention bysymmetrically disposing a uniformly thick layer of powder in a suitablecontainer around a cylindrical axially disposed core of suitablematerial, placing uniformly over the powder contaiuer surface a suitablecharge of high explosive and detonating it. In this way the inventionmay be applied in the formation of tubes from non-metal powders likegraphite, and from a wide variety of metal powders. It is particularlyuseful in the formation of tubes from titanium, aluminium, nickel, andiron powders and mixtures of these powders, and certain powdered steels.It also provides a ready means of forming hollow bodies from compactedmixtures of metal powders even if such mixtures cannot be alloyed andshaped by the normal fusion processes. Similarly the invention providesa means of joining tubes made from materials which are not readilyjoined by fusion. For example aluminium is notoriously difiicult to weldto other metals, but a tube consisting of a length of aluminiumconnected to a length of other metal can readily be formed by subjectingsuitably arranged portions of aluminium powder and the other powderedmetal to the process of the invention.

In a similar manner tubes may be formed which can be controllably variedin composition along their length or across their diameter. For exampletubes may be formed which consist of one metal at one end and anothermetal at the other end, and having an intervening portion containingboth metals in intimate admixtures, so that the composition is graduallyvaried along this intervening portion, the proportion of one metalincreasing and of the other metal decreasing along the length of thisportion of the tube. Tubes having an inner lining of one metalsurrounded by an outer layer of another metal can also be readily formedby the invention. This application is particularly advantageous wherethe inner layer is necessarily an expensive metal and the outer portion,which is used only to provide the necessary strength, is of a cheapermetal. Such types of metal tubes are commonly used in chemical plantsand neither can be formed by a fusion method. Tubes may also be readilyformed in which any portion of the length of the tube is made from ametal and the remainder is made from a non-metal powder such as graphiteor from mixtures of the metal and non-metal powder. A tube having anouter layer of a metal and an inner lining of a non-metallic materialmay be formed; conversely the outer layer of the tube may benon-metallic and the lining metallic.

Hollow bodies having a plurality of passages may be made by inserting aplurality of the aforedescribed cores i into the powdered material to becompacted so that each core is completely surrounded by the powderedmaterial. Thus, for example a cylindrical metal body may be formed witha plurality of passages whose axes are parallel to the axis of the body.

Referring to FIGURE 1 the core filling material 1 was contained in acardboard cylinder 2 having a wall thickness of 0.25 mm. axiallydisposed in the metal powder 3 contained in a thin-walled aluminium tube4 having a diameter of 5.5 cm. and a wall thickness of 0.05 cm. aportion of which latter is represented in the drawing as a front view.Thin Celluloid discs 5 were glued to the ends of the tubes 2 and tcontaining the core filling material 1 and the metal powder 3respectively, to render the tubes watertight. The explosive charge 6, aportion of which is also represented in the drawing as a front view, wasa single layer of plastic covered detonating fuse cord containing 44grains PETN per foot wound in helical manner tightly around the outersurface of the aluminium tube 4 containing the metal powder, so as tocompletely and evenly cover the said surface. The ends of four fuseleads7 equal in length were attached by means of adhesive tape to one end ofthe explosive charge 6 at points evenly spaced around the circumference.The other ends of the fuseleads 7 were attached by adhesive tape to oneend of a common fuselead 8 whose other end was attached to a detonatingmeans (not shown). The fuseleads 7 and the common fuselead 3 consistedof suitable lengths of plastic covered detonating fusecord containing 44grains iETN per foot. By arranging the fuseleads 7 in this manner theexplosive charge 6 was initiated at four points simultaneously therebyreducing the chance of getting uneven strains in the end portion of theexplosively formed tube which can happen when the charge is initiatedfrom one point only. Ideally the charge should be initiatedsimultaneously all around the circumferences at one end, but it is moredifficult to arrange such initiating means. However, as the detonationquickly evens out to become a steadily propagating detonation along thelength of the charge, only a small portion at the end of the explosivelyformed metal tube is afiected by the slightly uneven strains due tomultiple point initiation; for the size of the tube being formed in theexamples initiation at four points was found to be convenient. This endeffect could be eliminated by extending the explosive charge beyond thepowder at the end nearer the initiator, but usually it is moreconvenient to use an assembly as shown in the drawing and to remove anyportion at the end which is deformed or otherwise unsatisfactory. Thecomplete as sembly was placed inside a large container 9 containingwater 10, and was maintained in position therein with a supporting wire11, wrapped around a supporting bar 12 so that the explosive charge 6was surrounded with a thick layer of stemming water 10.

The core filling material 1, the core container 2, the

etal powder charge 3, the metal powder container 4 and the explosivecharge 6 were all 23 cm. in length. The explosive charge 6 consisted of7.5 m. of detonating fuse cord.

Examples 1 to 12 In the accompanying table details are given of thedimensions of metallic tubular elements compacted by assembling 12examples of combinations of core materials and metal powders as shown inFIGURE 1 and detonating the explosive layer surrounding the metalpowder.

The aluminum powder used m Examples 1-7 had a bulk density of 1.25 g./cc. and a particle size such that it all passed a 60 mesh B.S. sieve andwas retained on a mesh B.S. sieve. FIGURE 1:; illustrates a water coreas used in Example 6. FIGURE 1b illustrates an air core as used inFIGURE 7. The titanium powder used in Examples 8-12 had a bulk densityof 1.30 g./ cc. and all of it passed a 290 mesh B.S. sieve. The barytesused as the core filling material in Examples 2 and 9 had a bulk densityof 2.22 g./cc. and all of it passed a 240 mesh B.S.

sieve. The sodium chloride used as the core filling material in Examples1 and 8 had a bulk density of 1.22 g./ cc. and a particle size such thatall of it passed a 60 mesh B.S. sieve and was retained on a 100 meshB.S. sieve. The anhydrous sodium sulphate used as the core fillingmaterial in Examples 3 and had a bulk density of 1.19 g./ cc. and itsparticle size was such that all of it passed a 30 mesh B.S. sieve andwas retained on a 60 mesh B.S. sieve. The hydrated sodium sulphate usedas the core filling material in Examples 4 and 11 had a bulk density of0.89 g./ cc. and had a particle size such that all of it passed an 8mesh B.S. sieve and all of it was retained on a 30 mesh B.S. sieve.

On detonating the explosive the powdered materials 3 in these exampleswere in most cases formed into tubes having a uniform degree ofcompaction throughout. The dimensions of the core 1 and the layer ofpowdered material 3 in the shots which gave ruptured tubes in Examples1, 7, 8 and 112 indicate the minimum thickness of material which couldbe compacted by the technique used in these examples where the explosivelayer is adiacent to the layer of material being compacted. However, thewall thickness can be reduced by interposing a protective layer ofpowdered material between the explosive and the material which is beingformed into the tube. This technique is illustrated in Examples 14, and16. The inner and outer surf-aces of the compacted metal tubes were, inmost cases, somewhat uneven, but were easily smoothed by machining touniform dimensions. The dimensions given for the diameter of the coreafter compaction is in fact the diameter of the bore of the compactedmetal tube. When water or hydrated sodium sulphate were used as the corefilling material they separated from the metal tube in the process.

Example 13 In this example illustrated schematically in FIGURE 10, twotubes of circular cross-section were formed, of which a portion at oneend consisted of aluminium, a portion at the other end consisted oftitanium and the intermediate portion contained both these metals inadmixture the proportion of aluminium increasing and the proportion oftitanium decreasing along this intermediate portion from the endattached to the titanium portion. The tubes were formed by the processused in Examples 1-12 the disposition and lengths of the single axialcore, the metal powder 3 to be compacted, the containers 2 and 4 and thelayer of detonating fuse cord were the same as in the previous examples.The core filling in this example was sodium chloride of the kindpreviously used in Examples 1 and 8 and the core diameter was 1.5 cm.The outside diameter of the metal powder charges were 5.5 cm. The chargeof metal powder was varied along its length in the following mannerstarting from the bottom end.

Titanium powder 0-7 Mixture containing 9 parts Ti to 1 part Al by weight7-8 Mixture containing 8 parts Ti to 2 parts Al by weight 8-9 Mixturecontaining 7 parts Ti to 3 parts A1 by weight 9-10 Mixture containing 6parts Ti to 4 parts Al by weight 10-11 Mixture containing 5 parts Ti to5 parts Al by weight 11-12 Mixture containing 4 parts Ti to 6 parts Alby weight 12-13 Mixture containing 3 parts Ti to 7 parts A1 by weight13-14 Mixture containing 2 parts Ti to 8 parts Al by weight 14-15Mixture containing 1 part Ti to 9 parts A1 by weight 15-16 Aluminiumpowder 16-23 The aluminium powder was the same as that used in Examplesl-7; for one tube the titanium powder was the same as that used inExamples 8-12 and for the other it was of a particle size such that allof it passed a 16 mesh B.S. sieve and was retained on a mesh B.S. sieve.

The tubes formed on detonation of the explosive and subsequent removalof the co-re both had an external diameter of 3.5 cm. at the titaniumends and 4.1 cm. at the aluminium end, the internal diameters beingfairly uniformily 1.3 cm. all along the length of each tube. The tubeswere very firmly compacted, rigid, strong, free from cracks and wereeasily machined and polished at all parts.

Example 14 In this example a tube of circular cross-section andsubstantially uniform wall thickness was formed from powdered naturalgraphite of a particle size such that all of it passed a 100 mesh B.S.sieve. The technique used to form this tube was similar to that used inthe previous examples but in this case a layer of aluminium powder wasplaced around the layer of graphite to avoid the formation of cracks inthe tube produced. The lengths of the various items and theirdisposition before the detonation of the explosive were as in theprevious examples. In this case the outside diameter of the aluminiumpowder was 5.5 cm. and it was contained in the aluminium tube 4 asbefore. The core filling l was sodium chloride of the kind previouslyused and the outside diameter of the core was 1.7 cm. The outsidediameter of the annular graphite charge was 3.5 cm. The aluminium andgraphite layers were separated by a layer of paper 0.25 mm. thick. Thetube formed on firing the explosive and subsequent removal of the corehad an external diameter of 2.5 cm. and an internal diameter of 1.4 cm.the density of the compacted graphite being 2.13 g./cc. This tube wasuniformly compacted, free from cracks, rigid, strong and its surface waseasily polished. Such tubes are useful as nozzles for flame gases.

Example 15 In this example a tube of a circular cross-section anduniform wall thickness was formed from powdered silicon of a particlesize such that all of it passed a 100 mesh B.S. sieve and all of it wasretained on a 250 mesh B.S. sieve. The technique used was the same asthat used to form the graphite tube in Example 14, and the dispositionand the lengths of the various items in the assembly were the same asbefore. The core filling was sodium chloride as' used in Example 14 andthe core diameter was 1.7 cm. The external diameter of the annular layerof silicon placed around the core was 3.0 cm. and this layer wasseparated from the surrounding layer of aluminium powder by a layer ofpaper 0.25 mm. thick. The external diameter of the annular layer ofaluminium powder was 5.5 cm.

The tube of silicon formed on detonation of the explosive and subsequentremoval of the core had an external diameter of 2.5 cm. and an internaldiameter of 1.3 cm. It was uniformly compacted, rigid and free fromcracks.

Example 16 In this example a tube of circular cross-section and uniformwall thickness in which the composition was varied from aluminium at oneend to graphite at the other was prepared. The technique used to formthe tube was identical to that used in Examples 14 and 15, an annularlayer of powdered aluminium again being placed between the explosivelayer and the layer of powder to be compacted into the desired tube,these two layers being separated by a layer of paper 0.25 mm. thick. Thecore filling 1 was sodium chloride as in the previous example and theoutside diameter of the core was 1.7 cm. The charge of material to becompacted had an outside diameter of 3.5

cm. and its composition along its length starting from its bottom endwas:

Graphite O6.5 Mixture contai ring 8 parts graphite and 2 parts Al byweight 6.5-8.5 Mixture containing 6 parts graphite and parts Al byweight 53.5-10.5 Mixture containing 5 parts graphite and 5 parts Al byweight l0.5l2.5

Mixture containing 4- parts graphite and 6 parts Al by weight l2.5l4.5Mixture containing 2 parts graphite and 8 parts Al by weight 14.5l6.5Aluminium 16.5-23.

Example 17 In this example a tube of circular cross-section and uniformwall thickness was formed in which an outer annular layer of the tubewas made f om aluminium and an inner annular layer was made fromtitanium. The tech que used to form the tube was similar to that used inall the previous examples the disposition and the lengths of the core,the material to be compacted and the explosive layer being the same asin previous examples. The core filling in this case was sodium chlorideof the kind previously used and the core diameter was 1.5 cm. Thecylindrical core was surrounded by an an nular layer of titanium powderhaving an external diameter of 3.3 cm. and this in turn was surroundedby an annular layer of aluminium powder having an external diameter of5.5 cm., the two layers being in intimate contact at the interface. Thegrades of aluminium and titanium were those used in Examples 17 and 8-12respectively. The tube formed on detonation had an internal diameter of1.3 cm. and an external diameter of 4.0 cm. The inner layer of titaniumwas intimately joined to the outer layer of aluminium, the inner layerhaving an external diameter of approximately 2.5 cm. The tube wasuniformly compacted, free from cracks and was easily iachined andpolished to the desired dimensions.

Example 18 In this example a tube of circular crosssection and uniformwall thickness was formed having an outer annular layer of aluminium andan inner lining of graphite. The technique use was identical to thatused in Example 17. The core diameter in this example was 1.7 crn., theexternal diameter of the surrounding annular layer of powdered graphitewas 4.0 cm. and the external diameter of the annular layer of powderedaluminium was 5.5 cm. The tube formed on detonating the explosive andsubsequent removal of the core had an internal diameter of 1.5 cm. andan external diameter of 3.9 cm. The inner and outer layers wereintimately joined together, the inner layer having an external diameterof approximately 2.6 cm. The compacted mass had an overall density or"2.5 g./cc. The tube was uniformly compacted throughout, was free fromcracks and its surfaces were easily polished.

Example 19 In this example a tubular body having 3 separate internalpassages parallel to the longitudinal axis of the body was formed frompowdered aluminium oi the grade used in previous example The technique01 forming the body was similar to that used in the previous examplesbut instead cf using only one core entirely surrounded by the powderedmaterial to be compacted, three separate cylindrical cores were used andthese were so disposed within the powdered aluminium that their curvedsurfaces were entirely surrounded by a layer of the powdered aluminium.The cores were in fact placed so that in cross-section their centreswere symmetrically spaced on a circle of approximately 27 cm. indiameter. The cores consisted of sodium chloride of the kind used inprevious examples contained in a cardboard container having a wallthickness of 0.076 rum. and an external diameter of 1.1 cm. The outsidediameter of the charge of aluminium was 5.5 cm. As before this chargewas contained in a thin-walled aluminium tube 4 which was surrounded onits curved surface by a helically wound layer of detonating fuse 6 andthe whole assembly immersed in water before detonating the explosive.

The cylindrical body formed on detonating the explosive and subsequentremoval of the core had an external diameter of 4.2 cm. and had threecompletely separate passages formed along its length. The cross-sectionsof the passages were not true circles but were somewhat oval, theelongation being in a transverse direction with respect to thecross-sectional diameter of the formed body. The cross-sectionaldimensions of the passages were approximately 1.0 to 1.1 cm. across thewider part and 0.9 cm. across the narrower part. The cross-section ofthe centres or" the passages were evenly spaced on the circumference ofa circle having a diameter of 1.8 cm. and concentric with thecross-section of the formed body.

The mass appeared to be compacted uniformly throughout and the body wasfree from cracks.

Example 20 In this example a tube of circular cross-section and uniformwall thickness was formed from powdered natural graphite of the kindused in Example 15. The disposition of the explosive, the core and thesurrounding layer of powdered graphite is shown diagrammatically insectional elevation in FIG. 2 of the accompanying drawings. Thecylindrical core consisted of a filling of sodium chloride 23 as used inExample 1 contained in a tubular cardboard container 22 having a Wallthickness of 0.25 and 1.35 cm. external diameter and a length of 9.0 cm.This core was covered over its entire curved surface by an annular layerof powdered graphite 23 having an external diameter of 5.3 cm. containedin a tubular aluminium container 24 having a wall thickness of 0.5 mm.Thin Celluloid discs 25 were glued to the ends of the tubular containers22 and 24 to retain the powdered contents in position. The lower end ofcontainer 24 was placed on a lead plate 26 having a thickness of 3.0 cm.and surrounded on its curved and its upper surface by a layer ofexplosive 27 in powder form contained in a carboard container 23, theaverage thickness of this layer being 3.3 cm. The explosive compositionwas 8.3 parts nitroglycerine, 6.7 parts plant fibre, 56.2 parts ammoniumnitrate and 29 parts sodium chloride. The explosive was detonated bymeans of a detonator 29 placed in the explosive directly above the axialcore filling 21 as snown. On detonation of the explosive the powderedgraphite was uniformly compacted into a tube having an external diameterof 4.0 cm. and an internal diameter of 1.3 cm., which was free fromcracks.

Although in the examples given only short tubes were compacted, muchlonger hollow bodies could be formed by the process of the invention;for instance it is envisaged that lengths of up to 3 metres could beformed without difiiculty. The other dimensions of core diameters andthicknesses of the powder layers are also capable of wide variation.

FORMATION OF TUBES FROM METAL POWDER Outside diameter Core diameter, cm.of powdered metal, cm. Example Metal powder Core material Before AfterBefore After Compac- Compac- Gompae- Compaction tion tion tion 1. 7 1. 35. 5 4. l 2. 8 2. 4 5. 4. 0 1 Aluminium." Sodium Chloride 5 2 5 2 4. 25.2 3 2 BMW 5:; if; 2: 5 4:3 3 d0 Sodium Sulphate... 4 do SodiumSulphate 1. 7 1. 4 5. 5 3. 8

(Hydrated) 5 d0 Sodium Carbonate. 2.? 1. 6 d0 Water 8 2. 8 g 5 1. 7 0. 90 7 do All 5 (1) 5 a) l. 7 1. 2 5. 5 3. 5 8 Titanium Sodium Chlorlde 2.32.

3. 5 5. 5 1. 7 1. 4 5. 5 3. 5 9 d0 Barytes 3 2 g 3 1o do SodiumSulphate. 11 do Sodium Sulphate 1. 7 1. 4 5. 5 3. 5 (Hydrated) 1 7 1 G 55 3 5 12 do Water (1) 5 (1) 1 Tube ruptured.

What we claim is:

1. A process for the formation of a hollow shaped body from finelydivided powder capable of being compacted when subjected to thepressures generated by detonating explosives comprising embracing atleast one yieldable core consisting predominantly of non-explosivepourable material capable ultimately of being removed from the formedbody with a layer of the powder contained in a thin-walled container,the volume of said core embraced by said powder being capable of suddensubstantial reduction upon detonation of the explosive; positioning alayer of high explosive in proximity around a predetermined portion ofthe outer surface of the powder container and detonating the said highexplosive.

2. A process as claimed in claim 1 wherein each yieldable core consistsof a readily deformable thin walled container and a filling materialtherein.

3. A process as claimed in claim 2 in which the filling material is aparticulate solid which after the detonation is in a form capable offlow with respect to the deformed container.

4. A process as claimed in claim 2 in which the filling material is aliquid and in which said liquid is displaced upon detonation of theexplosive so as to achieve sudden substantial reduction in volume ofthat part of the core embraced by the powder.

5. A process as claimed in claim 2 in which the filling material is agas.

6. A process as claimed in claim 1 in which the composition of thefinely divided powder is varied from portion to portion so that a hollowbody having different compositions in different portions is formed.

References Cited in the file of this patent UNITED STATES PATENTS2,847,708 Harnjian et a1 Aug. 19, 1958 3,084,398 Swed Apr. 9, 1963FOREIGN PATENTS 833,673 Great Britain Apr. 27, 1960 847,775 GreatBritain Sept. 14, 1960 1,221,576 France Jan. 11, 1960

1. A PROCESS FOR THE FORMATION OF AHOLLOW SHAPED BODY FROM FINELYDIVIDED POWDER CAPABLE OF BEING COMPACTED WHEN SUBJECTED TO THEPRESSURES GENERATED BY DETONATING EXPLOSIVES COMPRISING EMBRACING ATLEAST ONE YIELDABLE CORE CONSISTING PREDOMINANTLY OF NON-EXPLOSIVEPOURABLE MATERIAL CAPABLE ULTIMATELY OF BEING REMOVED FROM THE FORMEDBODY WITH A LAYER OF THE POWDER CONTAINED INA THIN-WALLED CONTAINER, THEVOLUME OF SAID CORE EMBRACED BY SAID POWDER BEING CAPABLE OF SUDDENSUBSTANTIAL REDUCTION UPON DETONATION OF THE EXPLOSIVE; POSITIONING ALAYER OF HIGH EXPLOSIVE IN PROXIMITY AROUND A PREDETERMINED PORTION OFTHE OUTER SURFACE OF THE POWDER CONTAINED AND DETONATING THE SAID HIGHEXPLOSIVE.